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Abstract

We present a controlled Fano resonance in the mid-infrared (MIR) region from a kind of plasmonic metasurface consisting of a single-atom-thick surface layer with a periodic pattern of graphene nanostrip pairs on a dielectric substrate. Both the numerical and theoretical results indicate that the Fano resonance spectrum can be flexibly tailored through adjusting the geometrical parameters, such as the asymmetric distance and coupling gap between each pair of graphene nanostrips. Particularly, we achieve the dynamic tunability of the plasmonic Fano resonance spectrum by controlling the polarization of incident light and the Fermi level of graphene. The theoretical calculations agree well with the numerical simulations. These results could find significant applications in nanoscale light control and functional devices operating in the MIR region.

Figures (8)

Fig. 1 Schematic diagram of the plasmonic metasurface composed of a single-layer graphene array with a nanostrip pair in each cell unit on a dielectric substrate. The inset shows the graphene nanostrip pair in each unit cell. Here, P1: the pitch of graphene array in the x-axis direction, P2: the pitch of graphene array in the y-axis direction, g: the coupling gap between the graphene nanostrip pair, a: the asymmetric distance between the centers (dashed lines) of the graphene nanostrip pair, θ: the polarization angle of incident light, W1 (W2): the width of the graphene nanostrip 1 (2), L1 (L2): the length of the graphene nanostrip 1 (2).

Fig. 5 (a) Resonance frequency ω1 of the metasurface with different asymmetric distances a for the x- and y-polarized incident light. These results are obtained by fitting the simulation results in Fig. 3. The inset shows the detuning resonance frequency δ as a function of a. (b) Spectral profile of the term I in Eq. (4) for the x-polarized incident light with different a. The arrows denote the positions of Lorentzian resonance from the term II in Eq. (4). Here, P1 = 70 nm, P2 = 40 nm, W1 = 20 nm, L1 = 21 nm, W2 = 20 nm, L2 = 16 nm, and g = 6 nm.